When using an IATS merchant account ending in "99", the CVV2 (security code on back of credit card) is required by the payment processor as an added security measure. 

In order to correct the issue, please follow the steps below:

1.  Go to Revenue
2.  Select BBPS merchant accounts from the Configuration frame
3.  Highlight the default authorization account or whichever merchant account you are using to process the batch and select Edit
4.  Change the last two digits of the Gateway ID to 01 - 12 (Only the accounts ending in 99 require the CVV2 number)
5.  Save the changes and reprocess the credit cards